Charcot-Marie-Tooth

Charcot-Marie-Tooth (CMT) is an inherited neurological disorder, named for the three doctors who identified it in 1886 - Jean-Martin Charcot and Pierre Marie in France, and Howard Henry Tooth in England. CMT affects the peripheral nerves, which lie outside the brain and spinal cord. Peripheral nerves send signals to the muscles in the limbs and send sensations, such as touch and pain, back to the brain. CMT also is called hereditary motor and sensory neuropathy (HMSN) or peroneal muscular atrophy. It is the most common inherited neurologic disorder, occurring in one person for every 2,500 births.

+

Symptoms

Charcot-Marie-Tooth symptoms usually appear in adolescence or early adulthood, although it is possible for them to occur later. CMT affects motor nerves that send impulses to the muscles and sensory nerves that send impulses to the brain and spinal cord.

Symptoms may include:

  • Weakness in the foot and lower leg muscles
  • High arches
  • Hammer toes
  • Foot dropping
  • High-stepping gait
  • Tripping and falling
  • Lower leg taking on an inverted champagne-bottle appearance
  • Weakness and a loss of fine motor skills of the arms and hands

Symptoms progress gradually, and pain can be mild to severe. Occasionally, patients experience respiratory muscle weakness. The severity of symptoms varies between patients, even for members of the same family with the condition.


Causes and Risk Factors

Charcot-Marie-Tooth is inherited, and can be passed from one or both parents to a child. More than 70 genes have been linked to the disorder. In some cases, the gene mutation causing CMT has occurred spontaneously in patients’ DNA and is not connected to their parents. These patients may still pass the condition on to their children.

CMT is caused by a mutation in the genes responsible for proteins that affect axons, the nerve fibers sending electrical impulses between the brain and spinal cord to the rest of the body, or the myelin, a coating around the axons that increases the speed at which electrical signals travel.

Without an intact axon and myelin, peripheral nerve cells are unable to signal muscles. This results in muscle weakness and atrophy in the arms, legs, hands or feet. It also can cause problems relaying sensory information from the limbs back to the brain, lessening the ability to feel heat, cold and pain.

+

Diagnosis

Diagnosis of CMT begins with a standard patient history, family history and neurological examination. Patients will be asked about their symptoms, how long they’ve been experiencing symptoms and whether other family members have the disease or symptoms of CMT.

During the exam a physician will look for visual evidence as well as symptoms of weakened muscles or sensory loss. Patients may be asked to walk on their heels or press a leg against an opposing force to check for strength. The doctor also may do a knee-jerk test to see if the patient responds.

Genetic testing may be ordered, which requires a blood sample. DNA blood tests can detect many of the common gene defects responsible for CMT, although not all of them.

The physician may order electrodiagnostic tests, including electromyography (EMG) and nerve conduction studies. Using these tests together to measure the strength and speed of electrical impulses in the motor and sensory nerves and muscles can provide doctors with more complete information.

In some cases, a neurologist may perform a nerve biopsy to confirm the diagnosis. Nerve biopsy involves removing a small piece of peripheral nerve through an incision in the skin and examining it under a microscope.

+

Treatments

Charcot-Marie-Tooth is not fatal and most CMT patients have a normal life expectancy.

The most effective approach to diagnosis, family planning, physical therapy, bracing and orthopedic intervention can be accomplished with a specialized multidisciplinary approach, such as the one adopted by Charcot-Marie-Tooth/Hereditary Neuropathy Center at Cedars-Sinai.

While there currently is no cure, there are many types of therapies available to help patients cope with symptoms, maintain muscle strength and reduce pain.

The most common treatments for CMT are physical and occupational therapy. These therapies usually involve strengthening muscles, stretching muscles and ligaments, increasing stamina and moderate aerobic exercise to help maintain cardiovascular fitness and overall health. The sooner therapy begins, the greater the chance of delaying or reducing muscle atrophy as the disease progresses. Low-impact or no-impact exercises, such as biking or swimming, are more effective than activities such as walking or jogging that may put stress on fragile muscles and joints.

Many CMT patients require ankle braces and other orthopedic devices to maintain everyday mobility and prevent injury. Ankle braces can help prevent sprains by providing support and stability during activities such as walking or climbing stairs. High-top shoes or boots also can provide support for weak ankles. Thumb splints can help with hand weakness and loss of fine motor skills. Assistive devices should be used before disability sets in, because they may prevent muscle strain and reduce muscle weakening.

In some cases, orthopedic surgery can help reverse foot and joint defects to help CMT patients better deal with symptoms.